Interested in nature with a focus on birding and astronomy. Current project is a visual hunt for novae or exploding stars in the Galaxy from New York City. Got hooked on discovering things while birding and found that the hunt for novae in NYC is right up my alley.

Sunday, October 23, 2005

An important task is to identify all variable stars that can become as bright as the stars at the limit of the binocular limiting magnitude (BLM). For the Fujinon 10x70's this is currently ~9.4+. Searching at the BLM takes some effort so I've chosen an effective BLM (eBLM) of mag. 9.0.

For this purpose I set up an Excel file back in December of 2004 to filter on all known variables. This file contains all the stars in the General Catalog of Variable Stars (GCVS) which numbered 63,265 stars at the time. The filesize is ~37 megabytes.

The outline of the 'search area location chart' (SALC), in Right Ascension (RA) and Declination (Dec), is entered including a buffer zone. The buffer zone should include all stars in asterisms that extend beyond the boundaries of the main search area. This zone varies for each SALC.

This file identifies all variables in the SALC/buffer zone allowing one to filter on stars in any of the following categories:

• Spans - Stars that span the eBLM and change brightness by at least 3 tenths of a magnitude. These stars will become dimmer and grow brighter than the eBLM. These can easily be confused for a novae without knowing them beforehand. Four stars fall into this category for SALC 34N. See below for details. [Each variable has hyperlinks to two on-line catalogs. The 1st hyperlink after 'Name:' accesses SIMBAD & the last hyperlink accesses the GCVS.]

• Br.>.3 - Stars that change brightness by at least 3 tenths of a magnitude and are listed as always brighter than the eBLM. Four stars fall into this category. Only one, LX Per (8.1 - 8.9) comes close to the eBLM. See details below.

• Dim>.3 - Stars that change brightness by at least three tenths of a magnitude and are listed as always dimmer than the eBLM but no dimmer than three tenths of the eBLM. One star, NSV 15688, falls into this category ranging from 9.1 - 10.3 mag. See below for details.

Nova Persei 1901. About 4.5° NE of Algol. The first bright nova of the 20th Century, first noticed on February 21, 1901, by the amateur astronomer T.D. Anderson of Edinburgh, Scotland. At that time the star was of the 2nd magnitude, but within 2 days it had increased its light more than 6 times, and attained its maximum brilliancy of magnitude 0.2 on February 23.

However in 1974, a nova was found in Perseus by N. Sanduleak and announced on IAU Circular No. 2716, and later designated V400 Persei. Although the nova had already faded to magnitude 11 by the time it was found on an objective prism plate of November 9, 1974, there was a possibility that it had been brighter at an earlier date and been missed.